Teardrop shaped vehicular mirror

ABSTRACT

A vehicle mirror assembly having a housing and dome-type mirror lens. The lens has a first base footprint portion with a constant radius of curvature and a diameter, and a second base footprint portion comprised of an elliptical portion with a base major axis and a base minor axis. The mirror lens includes a first surface portion having a first surface radius and conforming to the first base footprint portion. The lens additionally includes a second surface portion conforming to the second base footprint portion. The second surface portion is comprised of a second surface major radius of curvature corresponding to a major surface axis and a second surface minor radius of curvature corresponding to a minor surface axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 11/422,131 filedJun. 5, 2006, which is a continuation-in-part of U.S. application Ser.No. 29/214660 filed on Oct. 6, 2004, entitled “Teardrop Shaped Mirror.”

TECHNICAL FIELD

The present invention relates generally to an exterior automotive mirrorassembly, and, more particularly to front-end mounted exteriorautomotive cross-over mirrors.

BACKGROUND OF THE INVENTION

Automotive mirror assemblies can play a vital role in vehicle operation.Placement of the vehicle operator within the vehicle structure oftenmakes direct line-of-sight to surrounding vehicle areas impractical. Yetsuch visual inspections of surrounding areas can provide the vehicleoperator with information necessary for proper vehicle operation. Asvehicle size increases, so often does the difficulty of accurate visualinspections. Vehicles, such as school buses, often utilize increasedvehicle sizes while requiring visual inspection of areas in front of andto the side of the vehicle. To this end, it is well known that vehiclemirrors may be front-end mounted to the vehicle to provide the widestpossible field of view around the vehicle.

Early attempts at widening the operator's field of view focused on theuse of convex mirrors. By increasing the size of the convex minor, itwas discovered that the field of view could be increased. Unfortunately,increasing the size of the convex mirror quickly becomes inefficient asthe mirror itself begins to become an obstruction to forward viewing. Toaccommodate the need for increased field of view, without negativelyimpacting mirror size, it is known that a domed mirror lens mayincorporate a varying radius of curvature along one of either the majoror minor axis. The varying radius of curvature achieves a compacted widefield of view or viewing area within minimal space such that the drivercan look forward of the vehicle with minimal blockage of vision. Thesemirrors with varying radius of curvature along one axis are commonlyreferred to as cross-over mirrors.

Although the use of cross-over mirror designs has proven highlysuccessful in the increase of viewing area while minimizing mirror size,present designs still can incorporate drawbacks. One of the drawbacks ofthese common cross-over mirror designs results from the distortion ofimages reflected in the mirror. Image distortion can result from thedepth of the dome and the varying radius of curvature of the lens. Thisdistortion can result in a reflected image of an object that is eitherelongated or widened depending on the orientation of the axes of themirror. Present designs, further limit the usefulness of such mirrors byrequiring the mirror to be designed to provide either a larger image ora wider field of view.

It would, therefore, be highly desirable to have a mirror assembly thatprovides a combination of larger image size and wider field of view. Itwould further be highly desirable to have a mirror assembly that couldprovide such a combination of viewing benefits while minimizingdistortion of images reflected in the mirror assembly.

SUMMARY OF THE INVENTION

A vehicle mirror assembly is provided. The vehicle mirror assemblyincludes a lens comprised of a first portion having a constant firstradius of curvature and a first diameter, and a second portion comprisedof an elliptical portion having a major axis and a minor axis. The shapeof the lens from both a top view and a side view comprises a portion ofa circular shape and a portion of an elliptical shape. The vehiclemirror assembly further includes a base or housing conforming to thelens footprint.

Other features of the present invention will become apparent when viewedin light of the detailed description of the preferred embodiment whentaken in conjunction with the attached drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view illustration of a “teardrop” shaped mirror lens inaccordance with the present invention.

FIG. 2 is perspective view illustration of the mirror lens illustratedin FIG. 1.

FIG. 3 is a cross-sectional illustration of the mirror lens illustratedin FIG. 2, the cross-section taken along the line 3-3 in FIG. 2 and inthe direction of the arrows.

FIG. 4 is a cross-sectional illustration of the mirror illustrated inFIG. 2, the cross-section taken along the line 4-4 in FIG. 2 and in thedirection of the arrows.

FIGS. 5 and 6 schematically depict the formation of the mirror lenscurvature in accordance with the present invention.

FIG. 7 depicts the field of view of a mirror made in accordance with thepresent invention.

FIG. 8 depicts a preferred use of the inventive lens mounted on a baseor housing.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to FIG. 1, which is an illustration of a mirror lens 10 inaccordance with the present invention. Although the mirror lens 10 isreferred to with the terminology “teardrop”, it should be understoodthat a variety of descriptors (such as “raindrop,” etc.) may be utilizedto describe the geometric configuration of the mirror lens 10. Themirror lens 10 generally has a convex dome shape and has an outerperipheral flange 18. The lens is typically mounted on a housing (suchas housing 100 in FIG. 8) forming a mirror assembly. The flange 18preferably seats on a mating flange of the housing and is mountedthereon. Preferably, a gasket or similar member is utilized to cover thetwo mating flanges. It should be understood that the flange on thehousing preferably comports to the configuration of the periphery of themirror lens 10.

The footprint of the lens 10 has a first base portion 20. The portion 20has a constant radius of curvature R₃ and a first diameter 24. Themirror lens 10 footprint further comprises a second base portion 26which is substantially elliptical in shape. The elliptical portion 26has a major axis 28 and a minor axis 30. The minor axis 30 of theelliptical portion 26 is coincident with and equal to the first diameter24 of the constant radius of the first portion 20. The major axis 28 ofthe elliptical portion 26 intersects the first diameter 24 atintersection point 32. The peripheral edge 16 of the lens 10circumscribes the first and second portions 20 and 26, as shown.

The dome of the mirror lens 10 is a partial ellipsoid that comprises afirst surface portion 34 which preferably has a constant first surfaceradius of curvature R₁ which is preferably proportionate andcomplementary to the first portion 20 of the lens footprint. The firstsurface portion 34 of the mirror lens preferably has a diameter toheight ratio of approximately 2.0:1.0 to about 2.5:1.0. In aparticularly preferred embodiment hereof, the first surface portion 34comprises one half of the mirror lens disclosed and claimed in U.S. Pat.No. 4,436,372, the disclosure of which is hereby incorporated byreference.

The dome of the mirror lens 10 has a second surface portion 36 which isintegral with the first surface portion 34 and is merged therewith at animaginary merge or split line 38. The second surface portion 36 of themirror lens 10 conforms to the conformation of the second or ellipticalportion 26 of the lens footprint. The second surface portion 36comprises a segment of an oval elliptical mirror lens having a majorsurface axis 40 which corresponds to the major axis 28 of the lens 10footprint. The second surface portion 36, also has a minor surface axis45 which corresponds to the minor axis 30 of the lens 12. The secondsurface portion 36 has a second surface major curvature R₂ which may beeither constant, varying, or continuously varying, as desired, along theextent thereof. R₃ is preferably a constant radius and is preferablyequal to and coincident with the radius R₁ Where R₂ has a varying radiusof curvature, the second surface portion 36 hereof preferably comprisesa segment of the oval elliptical mirror disclosed as in U.S. Pat. No.5,589,984, the disclosure of which is hereby incorporated by reference.

The present mirror lens 10 may be manufactured from any suitable“silverized” plastic by any suitable mode including thermoforming,injection molding, forming or the like. The materials of constructionare preferably selected such that upon formation there is no collapse atthe central portion of the lens to thus eliminate any potential ofnegative curvatures and distortion. The thermoforming process maycomprise either a forced air process or a vacuum forming process, bothof which are well known to the skilled artisan. Where the lens ismanufactured by a vacuum forming process, a vacuum chamber equipped withevacuation means is typically provided with an opening conforming to theshape of the minor lens 10 and over which is placed a sheet of softenedplastic. Thereafter, a vacuum is drawn within the chamber causing thesoftened plastic to “drop” within the chamber, cool, and then harden.Upon cooling and hardening, the plastic sheet assumes a shape whichconforms to that of the lens 10. Forced air thermoforming is similar tovacuum forming, in that heat pressurized air is utilized to cause thesoftened, warm plastic sheet to form over an opening. Injection moldingmay additionally be utilized in order to mold the lens 10 to desiredspecifications. It should be understood, however, that although specificmanufacturing methodologies have been described, a variety ofmanufacturing methodologies may be utilized to implement the presentinvention.

Using any of the aforementioned manufacturing processes, it ispreferable that the mirror lens 10 is formed, using the first footprintportion 20 with a constant radius R₃ and the second footprint portion 26shaped as an elliptical portion. The first portion 34 has a constantradius R₁ (which preferably is the same as R₃), and the second surfaceportion 36 has a varying radius of curvature R₂ along the major surfaceaxis 40. The second surface portion 36 also has a constant radius ofcurvature R₁ across the minor surface axis 45 thereof. Regardless oforientation, the mirror lens 10 provides a field of view which providesimproved imaging with a reduction in the distortion of the image thereofIt should be noted that at the apex or intersection 42 of the surfaceaxes 40, 45, the lens 10 preferably has a diameter to height rationranging from about 2.0 to about 2.5 and, most preferably from about 2.1to about 2.5.

The present lens or dome 10, which resembles a raindrop or teardrop,provides a larger field of view in the first surface portion 34 (theround side) and a larger image size on the second surface portion 36(the elliptical side). In other words, by practicing the presentinvention, the base minor axis 30 of the mirror 10 is being shifted fromthe center of the mirror, as measured along the base major axis 28 ofthe lens 10, by a distance of approximately one-tenth to one-fourth ofthe length of the major axis 28. This shifting enables the difference inthe observable images in the mirror, i.e., large field of view versuslarge image.

It should be further noted with respect hereto that in manufacturing thepresent mirror the thermoplastic resin used to form the lens 10 may havea colorant or dye incorporated therewith such that the resulting lenscomprises a colored reflective surface. Although the color or hue ischosen at the option of the user, preferred colors include a legal bluehue, amber and the like. Optionally, a glare reducing color can bechosen. Because the color is imparted to the resin which is used to formthe lens 10, it is seen through the silverized or reflective layer whichis deposited onto the surface of the lens or dome. Although a particularembodiment has thus been described, it should be understood that a widevariety of configurations are contemplated.

FIGS. 5 and 6 schematically depict the manner in which the shape of anembodiment of the inventive mirror lens 50 is formed from circular andelliptical figures. From a top or plan view, as shown in FIG. 5, thelens 50 (depicted generally in dashed lines) is formed fromapproximately one-half of a circular shape 52 and approximately one-halfof an ellipse 54. The two shapes 52 and 54 are tangential to each otherat points 56 and 58 which are the opposite ends of both the diameter Dof circular shape 52 and the length of the minor axis A-1 of the ellipse54. The major axis of the elliptical shape 54 is indicated by thereference A-2.

From a side or cross-sectional view, as shown in FIG. 6, the shape ofthe mirror lens 50 (again depicted generally in dashed lines) is formedfrom a portion 60 of a circular shape 62 and a portion 64 of anelliptical shape 66. The two shapes 62 and 66 are tangential to eachother at point 70 which is approximately at one end of the major axis Mof the ellipse 66. A flange or rim 72 on the mirror lens 50 is alsoincluded in FIG. 6.

The large field of view of the mirror lens 50 formed in accordance withthe present invention is shown in FIG. 7 and indicated generally by thereference numeral 80 and the angle θ. As indicated, the field of view ismore than 180° and is wider and larger in one direction 82 than theother 84. The direction 82 is angle X behind and beyond the edge of thelens 50 (formed by reference plane 90), while the direction 84 is lessthan the plane 90 by angle Y. The valves of angles X and Y will dependon the sizes and shapes of the circular and elliptical figures fromwhich the mirror lens is formed.

FIG. 8 illustrates the mounting of the mirror lens 50 on the base orhousing 100 thereby forming a mirror assembly 110. The base or housingcan be of any conventional material, such as metal or plastic, in usetoday for the backs of vehicle mirrors, and can be formed in anyconventional manner. The base 100 has the same footprint shape as thelens 50 and has a perimeter flange member 102 which mates with theperimeter flange 72 on the lens 50. Preferably, a rubber or elastomericgasket member 104 is positioned around the mirror assembly which acts tohold the lens and base together. The gasket member also seals the insideof the mirror assembly from environmental conditions and adds a pleasingand finished appearance to the assembly.

It is also possible to include a mounting mechanism (not shown), such asa conventional ball-type or tunnel type mounting mechanism, on the baseor housing 100 in order to mount or attach the mirror assembly to avehicle or other structure.

While particular embodiments of the invention have been shown anddescribed, numerous variations and alternative embodiments will occur tothose skilled in the arm. Accordingly, it is intended that the inventionbe limited only in terms of the appended claims.

What is claimed is:
 1. A mirror assembly comprising: (a) a base member;(b) a dome-type mirror lens connected to said base member, said lenscomprising; (i) a first portion comprising a portion of a sphere havinga substantially constant first radius of curvature throughout, and; (ii)a second portion comprising a portion of an oval ellipsoid having asecond radius of curvature along the minor axis substantially the sameas the first radius of curvature of said first portion, and having athird radius of curvature along the major axis, the third radius ofcurvature being greater than said first and second radii of curvature.2. A mirror assembly as described in claim 1 wherein said minor axis isshifted from a center of the length of said base member by a distance ofapproximately one-tenth to one-fourth the length of said major axis. 3.A mirror assembly as described in claim 1 wherein said first portion isintegral and merged with said second portion along a merge line.
 4. Amirror assembly as described in claim 1 wherein said third radius ofcurvature comprises a varying radius of curvature.
 5. A mirror assemblyas described in claim 4 wherein said third radius of curvature comprisesa varying radius of curvature which decreases along the outer surface ofsaid second portion toward the outer perimetral edge.
 6. A mirrorassembly as described in claim 1 wherein said first portion produces alarger field of view than said second portion and said second portionproduces a larger image view than said first portion.